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Versions: 00 01 02 03 04 05 RFC 7651

IPSECME WG                                                 A. Dodd-Noble
Internet-Draft                                             S. Gundavelli
Intended status: Informational                                     Cisco
Expires: October 25, 2015                                    J. Korhonen
                                                             F. Baboescu
                                                    Broadcom Corporation
                                                                 B. Weis
                                                                   Cisco
                                                          April 23, 2015


                       3GPP IMS Option for IKEv2
            draft-gundavelli-ipsecme-3gpp-ims-options-05.txt

Abstract

   This document defines two new configuration attributes for Internet
   Key Exchange Protocol version 2 (IKEv2).  These attributes can be
   used for carrying the IPv4 address and IPv6 address of the Proxy-Call
   Session Control Function (P-CSCF).  When an IPsec gateway delivers
   these attributes to an IPsec client, the IPsec client can obtain the
   IPv4 and/or IPv6 address of the P-CSCF server located in the 3GPP
   network.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 25, 2015.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions and Terminology . . . . . . . . . . . . . . . . . . 4
     2.1.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4
     2.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  P_CSCF_IP4_ADDRESS Configuration Attribute  . . . . . . . . . . 5
   4.  P_CSCF_IP6_ADDRESS Configuration Attribute  . . . . . . . . . . 5
   5.  Example Scenario  . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9


























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1.  Introduction

   The Third Generation Partnership Project (3GPP) S2b reference point
   [TS23402], specified by the 3GPP system architecture defines a
   mechanism for allowing a mobile node (MN) attached in an untrusted
   non-3GPP IP Access Network to securely connect to a 3GPP network and
   access IP services.  In this scenario, the mobile node establishes an
   IPsec ESP tunnel [RFC4303] to the security gateway called evolved
   packet data gateway (ePDG) and which in turn establishes a Proxy
   Mobile IPv6 (PMIPv6) [RFC5213] or GPRS Tunneling Protocol (GTP)
   [TS23402] tunnel to the packet data gateway (PGW) [TS23402] where the
   mobile node's session is anchored.

   The below figure shows the interworking option for non-3GPP access
   over an untrusted-access network.  The mobile access gateway (MAG)
   and the local mobility anchor (LMA) functions are defined in
   [RFC5213].  The ePDG and PGW functions are defined in [TS23402].
   IPsec ESP tunnel is between the MN and the ePDG and PMIP or GTP
   tunnel between the ePDG and the PGW.



                                 +------------+
                                 |    ePDG    |
                                 | +--------+ |
   +------+        _----_        | | IPsec  | |      _----_      +-----+
   |  MN  |      _(      )_      | | Module | |    _(      )_    | LMA |
   |      |<====( Internet )=====| +--------+ |===( Operator )===|(PGW)|
   +------+      (_      _)      |      :     |    (_Network_)   +-----+
                   '----'        | +--------+ |      '----'
                  IPsec Tunnel   | | PMIPv6 | |  PMIPv6/GTP Tunnel
                                 | |   MAG  | |
                                 | +--------+ |
                                 +------------+

      |<------------ IKEv2/IPsec ------> | <------ PMIPv6/GTP ----->|


           Figure 1: Exchange of IPv4 Traffic Offload Selectors

   A mobile node in this scenario may potentially need to access the IP
   Multimedia Subsystem (IMS) services in the 3GPP network [TS23228] and
   [TS24229].  Currently, there are no attributes in IKEv2 [RFC7296]
   that can be used for carrying these information elements.  In the
   absence of these attributes the mobile node needs to be statically
   configured with this information and this is proving to be an
   operational challenge.  Any other approaches such as using DNS, or
   DHCP for discovering these functions would result in obtaining



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   configuration in the access network and not in the home network.
   Given that the above referenced 3GPP interface is primarily for
   allowing the mobile node to connect to the 3GPP network through an
   untrusted-access network, the access network may not have any
   relation with the home network provider and may be unable to deliver
   the mobile node's home network configuration.

   This specification therefore defines two new IKEv2 attributes
   [RFC7296] that allows an IPsec gateway to provide the IPv4 and/or
   IPv6 address of the P-CSCF server.  These attributes can be exchanged
   by IKEv2 peers as part of the configuration payload exchange.  The
   attributes follow the configuration attribute format defined in
   Section 3.15.1 of [RFC7296].  Furthermore, providing the P-CSCF
   server address(es) in IKEv2 as standard attribute(s) enables clients
   to directly access IMS services behind a VPN gateway without going
   through the 3GPP specific interfaces.


2.  Conventions and Terminology

2.1.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.2.  Terminology

   All the IKEv2 related terms used in this document are to be
   interpreted as defined in [RFC7296] and [RFC5739].  All the mobility
   related terms are to interpreted as defined in [RFC5213] and
   [RFC5844].  Additionally, this document uses the following terms:

   Proxy-Call Session Control Function (P-CSCF)

      The P-CSCF is the entry point to the 3GPP IMS (IP Multimedia
      Subsystem) and serves as the SIP outbound proxy for the mobile
      node.  The mobile node performs SIP registration to 3GPP IMS and
      initiates SIP sessions via a P-CSCF.

   Evolved Packet Data Gateway (ePDG)

      Its is a security gateway defined by the 3GPP system architecture.
      The protocol interfaces it supports include IKEv2 [RFC7296].







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3.  P_CSCF_IP4_ADDRESS Configuration Attribute

   The P_CSCF_IP4_ADDRESS configuration attribute is formatted as
   follows:


    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|        Attribute Type       |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         IPv4 Address                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 2: IPv4 Address of P-CSCF

   Reserved (1 bit)
      Refer to IKEv2 specification

   Attribute Type (15 bits)
      <IANA-1>

   Length (2 octets)
      Length of the IPv4 address field that follows.  Possible values
      are (0) and (4).  A value of (4) indicates the size of the 4-octet
      IPv4 address that follows.  A value of (0) indicates that its a
      empty attribute with zero-length IPv4 address field, primarily
      used as a request indicator.

   IPv4 Address (4 octets)
      An IPv4 address of the P-CSCF server.

   The P_CSCF_IP4_ADDRESS configuration attribute provides an IPv4
   address of a P-CSCF server within the network.  If an instance of an
   empty P_CSCF_IP4_ADDRESS attribute with zero-length IPv4 Address
   field is included by mobile node, the responder MAY respond with
   zero, one or more P_CSCF_IP4_ADDRESS attributes.  If several
   P_CSCF_IP4_ADDRESS attributes are provided in one IKEv2 message,
   there is no implied order among the P_CSCF_IP4_ADDRESS attributes.
   However, a system architecture using this specification may be able
   to enforce some order at both the peers.


4.  P_CSCF_IP6_ADDRESS Configuration Attribute

   The P_CSCF_IP6_ADDRESS configuration attribute is formatted as
   follows:



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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |R|        Attribute Type       |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                                                               |
   |                          IPv6 Address                         |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 3: IPv6 Address of P-CSCF

   Reserved (1 bit)
      Refer to IKEv2 specification

   Attribute Type (15 bits)
      <IANA-1>

   Length (2 octets)
      Length of the IPv6 address field that follows.  Possible values
      are (0) and (16).  A value is (16) indicates the size of the 16-
      octet IPv6 address that follows.  A value of (0) indicates that
      its a empty attribute with zero-length IPv6 address field,
      primarily used as a request indicator.

   IPv6 Address (16 octets)
      An IPv6 address of the P-CSCF server.

   The P_CSCF_IP6_ADDRESS configuration attribute provides an IPv6
   address of a P-CSCF server within the network.  If an instance of an
   empty P_CSCF_IP6_ADDRESS attribute with zero-length IPv6 Address
   field is included by mobile node, the responder MAY respond with
   zero, one or more P_CSCF_IP6_ADDRESS attributes.  If several
   P_CSCF_IP6_ADDRESS attributes are provided in one IKEv2 message,
   there is no implied order among the P_CSCF_IP6_ADDRESS attributes.
   However, a system architecture using this specification may be able
   to enforce some order at both the peers.


5.  Example Scenario

   The mobile node MAY request the IP address of an P-CSCF server as
   shown below.






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         Client      Gateway
        --------    ---------

         HDR(IKE_SA_INIT), SAi1, KEi, Ni  -->

                  <--  HDR(IKE_SA_INIT), SAr1, KEr, Nr, [CERTREQ]

         HDR(IKE_AUTH),
         SK { IDi, CERT, [CERTREQ], AUTH, [IDr],
              CP(CFG_REQUEST) =
                 { INTERNAL_IP4_ADDRESS(),
                   INTERNAL_IP4_DNS(),
                   P_CSCF_IP4_ADDRESS() }, SAi2,
              TSi = (0, 0-65535, 0.0.0.0-255.255.255.255),
              TSr = (0, 0-65535, 0.0.0.0-255.255.255.255) }  -->

                <--  HDR(IKE_AUTH),
                     SK { IDr, CERT, AUTH,
                          CP(CFG_REPLY) =
                             { INTERNAL_IP4_ADDRESS(192.0.2.234),
                               P_CSCF_IP4_ADDRESS(192.0.2.1),
                               P_CSCF_IP4_ADDRESS(192.0.2.4),
                               INTERNAL_IP4_DNS(198.51.100.33) },
                          SAr2,
                          TSi = (0, 0-65535, 192.0.2.234-192.0.2.234),
                          TSr = (0, 0-65535, 0.0.0.0-255.255.255.255) }


                    Figure 4: P-CSCF Attribute Exchange


6.  IANA Considerations

   This document requires the following two IANA actions.

   o  Action-1: This specification defines a new IKEv2 attribute for
      carrying the IPv4 address of P-CSCF server.  This attribute is
      defined in Section 3.  The Type value for this Attribute needs to
      be assigned from the IKEv2 Configuration Payload Attribute Types
      namespace defined in [RFC7296].

   o  Action-2: This specification defines a new IKEv2 attribute for
      carrying the IPv6 address of P-CSCF server.  This attribute is
      defined in Section 4.  The Type value for this Attribute needs to
      be assigned from the IKEv2 Configuration Payload Attribute Types
      namespace defined in [RFC7296].





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7.  Security Considerations

   This document is an extension to IKEv2 [RFC7296] and therefore it
   inherits all the security properties of IKEv2.

   The two new IKEv2 attributes defined in this specification are for
   carrying the IPv4 and IPv6 address of the P-CSCF server.  These
   attributes can be exchanged by IKE peers as part of the configuration
   payload and the currently defined IKEv2 security framework provides
   the needed integrity and privacy protection for these attributes.
   Therefore this specification does not introduce any new security
   vulnerabilities.


8.  Acknowledgements

   The Authors would like to specially thank Tero Kivinen for the
   detailed reviews.  Authors would also like to thank Vojislav Vucetic,
   Heather Sze, Sebastian Speicher, Maulik Vaidya, Ivo Sedlacek,
   Pierrick Siete and Hui Deng for all the discussions related to this
   topic.


9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, October 2014.

9.2.  Informative References

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

   [RFC5739]  Eronen, P., Laganier, J., and C. Madson, "IPv6
              Configuration in Internet Key Exchange Protocol Version 2
              (IKEv2)", RFC 5739, February 2010.

   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", RFC 5844, May 2010.



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   [TS23228]  3GPP, "Service requirements for the Internet Protocol (IP)
              multimedia core network subsystem (IMS); Stage 1", 2014.

   [TS23402]  3GPP, "Architecture enhancements for non-3GPP accesses",
              2014.

   [TS24229]  3GPP, "IP multimedia call control protocol based on
              Session Initiation Protocol (SIP) and Session Description
              Protocol (SDP); Stage 3", 2014.


Authors' Addresses

   Aeneas Noble
   Cisco
   30 International Pl
   TEWKSBURY, MASSACHUSETTS  95134
   USA

   Email: noblea@cisco.com


   Sri Gundavelli
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: sgundave@cisco.com


   Jouni Korhonen
   Broadcom Corporation
   Porkkalankatu 24
   Helsinki  FIN-00180
   Finland

   Email: jouni.nospam@gmail.com


   Florin Baboescu
   Broadcom Corporation
   100 Mathilda Place
   Sunnyvale, CA  94086
   USA

   Email: baboescu@broadcom.com>




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   Brian Weis
   Cisco
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: bew@cisco.com












































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